Relay device, time synchronization system, and program

Abstract

A relay device includes a device internal clock to indicate time; a memory to store information; a communication unit to transmit and receive a signal including a synchronization signal and a normal signal to and from a master and a slave. Further, there is a retention time processing unit to store synchronization signal information indicating the synchronization signal received by the communication unit in the memory and extract the synchronization signal information from the memory when a retention setting time longer than a first predetermined time elapses from the reception of the synchronization signal by using the time indicated by the device internal clock; and a transmission signal control unit to control the communication unit to stop transmitting the normal signal when the first predetermined time elapses from the reception of the synchronization signal and transmit the synchronization signal indicating the synchronization signal information.

1 . A relay device comprising:
 a device internal clock to indicate time;   a memory to store information;   communication circuitry configured to transmit and receive a signal including a synchronization signal and a normal signal to and from a master and a slave;   retention time processing circuitry configured to store synchronization signal information indicating the synchronization signal received by the communication circuitry in the memory and extract the synchronization signal information from the memory when a retention setting time longer than a first predetermined time elapses from the reception of the synchronization signal by using the time indicated by the device internal clock; and   transmission signal control circuitry configured to control the communication circuitry to stop transmitting the normal signal when the first predetermined time elapses from the reception of the synchronization signal and transmit the synchronization signal indicating the synchronization signal information when the synchronization signal information is extracted from the memory.   
     
     
         2 . The relay device according to  claim 1 , wherein
 the first predetermined time includes a first forward-path predetermined time and a first return-path predetermined time,   the retention setting time includes a forward-path retention setting time and a return-path retention setting time,   the communication circuitry includes a first reception circuitry configured to receive the signal from the master and a second reception circuitry configured to receive the signal from the slave,   the memory includes a first memory and a second memory,   the retention time processing circuity includes first retention time processing circuitry and second retention time processing circuitry,   the first retention time processing circuitry stores the synchronization signal information indicating the synchronization signal received by the first reception circuitry in the first memory and extracts the synchronization signal information stored in the first memory when the forward-path retention setting time longer than the first forward-path predetermined time elapses from the reception of the synchronization signal, and   the second retention time processing circuitry stores the synchronization signal information indicating the synchronization signal received by the second reception circuitry in the second memory and extracts the synchronization signal information stored in the second memory when the return-path retention setting time longer than the first return-path predetermined time elapses from the reception of the synchronization signal.   
     
     
         3 . The relay device according to  claim 2 , wherein the return-path retention setting time is the same as the forward-path retention setting time. 
     
     
         4 . The relay device according to  claim 1 , wherein when a second predetermined time longer than the retention setting time elapses from the reception of the synchronization signal, the transmission signal control circuitry controls the communication circuitry to start transmitting the normal signal received by the communication circuitry. 
     
     
         5 . A time synchronization system comprising:
 the relay device according to  claim 1 ; and   a master and slave configured to communicate with the relay device, wherein   the communication circuitry transmits, from the master to the slave, a master time signal indicating a master time at which the master transmits and receives the synchronization signal, and   the slave includes a slave internal clock and corrects the slave internal clock on the basis of a slave time indicating a time at which the slave transmits and receives the synchronization signal, the master time, and the retention setting time.   
     
     
         6 . The time synchronization system according to  claim 5 , wherein the slave corrects the slave internal clock further on the basis of a communication time that is a period of time during which the synchronization signal is propagated through a communication network. 
     
     
         7 . A program for causing a computer to function as the relay device according to  claim 1 .